An AC surface discharge panel as a typical plasma display panel (hereinafter, abbreviated as a “panel”) includes a front panel and a rear panel disposed facing each other with a large number of discharge cells provided therebetween. The front panel has a plurality of display electrode pairs, each composed of a pair of scan electrode and sustain electrode, formed in parallel to each other on a front glass substrate, and has a dielectric layer and a protective layer formed so as to cover the display electrode pairs. The rear panel includes a plurality of data electrodes formed in parallel to each other on a rear glass substrate, a dielectric layer formed so as to cover the data electrodes, a plurality of barrier ribs formed in parallel to the data electrodes on the dielectric layer. A phosphor layer is formed on the top surface of the dielectric layer and the side surface of the barrier ribs. The front panel and the rear panel are disposed facing each other so that the display electrode pairs three-dimensionally intersect with the data electrodes, and sealed to each other. The discharge space inside thereof is filled with a discharge gas including, for example, xenon at the partial pressure ratio of 5%. Herein, a discharge cell is formed in a portion where the display electrode pair and the data electrode face each other. In a panel having such a configuration, ultraviolet light is generated by gas discharge in each discharge cell, and this ultraviolet light excites phosphor layers for red (R), green (G) and blue (B) to cause light emission for color display.
As a method for driving a panel, a subfield method is generally employed. The subfield method divides one field period into a plurality of subfields, and carries out gradation display by a combination of subfields to emit light.
Each subfield includes an initializing period, an address period, and a sustain period. In the initializing period, initializing discharge is generated and wall charge necessary for a subsequent address operation is formed on each electrode, and priming particles (priming for discharge=excited particles) for stably causing address discharge are generated. In the address period, an address pulse voltage is selectively applied to a discharge cell to be displayed so as to cause address discharge, thus forming wall charge (hereinafter, this operation is also referred to as “address”). In the sustain period, a sustain pulse voltage is applied alternately to the display electrode pair composed of the scan electrode and the sustain electrode so as to cause sustain discharge in a discharge cell in which address discharge has been generated. Thus, a phosphor layer of the corresponding discharge cell is allowed to emit light so as to carry out an image display.
Furthermore, among the subfield methods, there is disclosed a driving method of causing initializing discharge by using a gently changing voltage waveform, further selectively causing initializing discharge with respect to a discharge cell in which sustain discharge has been generated, and thereby reducing light emission that is not related to the gradation display as much as possible to improve a contrast ratio.
Specifically, an all-cell initializing operation for causing initializing discharge in all discharge cells is carried out in the initializing period of one subfield in the plurality of subfields, and a selective initializing operation for causing initializing discharge only in a discharge cell in which sustain discharge has been carried out in the immediately preceding sustain period is carried out in the initializing period of the other subfields. With such driving, brightness in a black display region (hereinafter, abbreviated as “black brightness”) changing depending on light emission that is not related to an image display is only feeble light emission in the all-cell initializing operation. Thus, an image display with a high contrast becomes possible (see, for example, patent document 1).
Furthermore, the above-mentioned patent document 1 also discloses so-called narrow width erase discharge in which the pulse width of the last sustain pulse in the sustain period is made to be shorter than the pulse width of other sustain pulses so as to relieve the potential difference by wall charge between the display electrode pairs. This narrow width erase discharge can stabilize an address operation in an address period in the subsequent subfield, and thus, a plasma display device with a high contrast ratio can be realized.
With recent trend toward high resolution of a panel, a discharge cell is becoming finer. It is confirmed that, in the finer discharge cells, a phenomenon called charge drop off in which wall charge is lost easily occurs. When the charge drop off occurs, discharge failure occurs, thus deteriorating the quality of image display or increasing the applied voltage necessary to cause discharge.
One of the main reasons of the charge drop off is discharge variation at the time of address operation. For example, when the discharge variation at the time of the address operation is large and strong address discharge is generated, in a place where a discharge cell to emit light and a discharge cell that does not emit light are adjacent to each other, the discharge cell to emit light may deprive wall charge from the discharge cell that does not emit light, which may lead to the charge drop off.
Therefore, it is important to generate address discharge as stably as possible in order to prevent the charge drop off.
On the other hand, recently, panels having a larger screen and a higher resolution have been developed. Accordingly, a driving impedance of a panel tends to increase. When the driving impedance increases, a waveform distortion such as ringing easily occurs in a drive waveform generated from a drive circuit of the panel. The above-mentioned narrow width erase discharge is generated for stabilizing an address operation in the subsequent subfield. However, for example, when a waveform distortion occurs in a drive waveform for causing this narrow width erase discharge, the narrow width erase discharge itself may strongly occur. In such a case, it is difficult to stably generate subsequent address discharge.
[Patent document 1] Japanese Patent Application Unexamined Publication No. 2000-242224